The medal of the Immaculate Conception.
November 27 marks the feast of the Miraculous Medal, otherwise known as the medal of the Immaculate Conception. Though the feast honors the Immaculate Conception of the Blessed Virgin Mary, the memorial commemorates the anniversary of the apparition of the Mother of God to St. Catherine Laboure in Paris in 1830, wherein Our Lady showed the nun the medal she wished to be made for those to wear seeking her aid and protection. The Blessed Virgin spoke to Catherine: “Have a medal struck upon this model. Those who wear it will receive great graces, especially if they wear it around the neck.” Countless miracles followed, hence the name, the Miraculous Medal. The story here.
O Mary conceived without sin, pray for us who have recourse to thee.
Paradise of the children of Eve, refuge of sinners, consolation of the afflicted, solace in sorrow, light in darkness, enclosure for the homeless, rest for the weary, health of the sick, gate of heaven....
Pray for us who have recourse to thee, and for those who do not have recourse to thee, especially the enemies of the Church and those recommended to thee. Amen
O Mary, may your holy and Immaculate Conception be my refuge, my anchorage, and the way that will lead me to God. Amen.
O Mary! By your Holy and Immaculate Conception, make my body pure and my spirit holy. Amen.
The medal really is miraculous, hence the name.
As Our Lady instructed St. Catherine:
St Therese used to sneak these medals into the lining of the coats of workmen who came into the Carmel to do repairs. I have done the same - I also hide the medal in works of art which I make. When we do this we pray the prayer on the medal for the recipient. It's not a talisman or magic, but rather a blessed sacramental - a sign of Our Lady's presence and protection. Our prayer for others is an act of faith and love united to the prayer of Our Lady, of the Church, of Christ who makes intercession for us.
The story of St. Catherine here.